Chemical Forums
Chemistry Forums for Students => High School Chemistry Forum => Topic started by: baggravation on July 26, 2009, 01:27:50 AM
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When someone gets carbon monoxide poisoning,everyone says that the best treatment is putting a 100% oxygen mask on the person. Why do that?
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First you need to consider how carbon monoxide poisons you.
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First you need to consider how carbon monoxide poisons you.
When carbon monoxide is inhaled, it goes through the lungs then into the hemoglobin molecules of red blood cells. Carbon monoxide binds to hemoglobin at the same site as the oxygen, forming carboxyhemoglobin. Carboxyhemoglobin interferes with the oxygen transport and gas exchange of the red blood cells. As a result, the body becomes oxygen-starved, which can result in death.
So you pretty much give the body oxygen to stop the starvation. Is that just it? What happens to the carbon monoxide that entered the body?
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Carbon monoxide binds to hemoglobin at the same site as the oxygen, forming carboxyhemoglobin.
Good. Now, think in terms of Le Chatelier's principle.
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Carbon monoxide binds to hemoglobin at the same site as the oxygen, forming carboxyhemoglobin.
Good. Now, think in terms of Le Chatelier's principle.
Well I'm not too sure what to say after this. I don't understand what happens when you add oxygen. CO still reacts more readily with Hb. What happens to the CO in the body?
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As an aside, here's a fun fact completely irrelevant to this question. This is an excerpt from a morbidly delightful book I read not too long ago: Molecules of Murder: Criminal Molecules and Classical Cases. (http://www.amazon.com/Molecules-Murder-Criminal-Classic-Cases/dp/0854049657)
Exposure to small but constant amounts of carbon monoxide over a period of time produces a variety of symptoms, which may at first not be recognized as having been caused by this gas. In addition to headaches and muscular pain there can be depression, chronic fatigue syndrome, and even hallucinations. In some instances this has been used to explain experiences associated with haunted houses, such as feelings of dread, sudden shivering, strange noises resembling footsteps, and even some unexplained deaths. In certain cases the haunting has been traced to a defective boiler or heater which is emitting carbon monoxide. Once the fault has been corrected these phantoms of the night are generally exorcised. The Victorian era was a golden age for haunting and weird manifestations, and one wonders to what extent this was a consequence of the widespread use of town gas (ed: http://en.wikipedia.org/wiki/Natural_gas#Town_gas) for lighting and cooking. this was piped to most homes and buildings and it inevitably contained a few percent of carbon monoxide. the replacement of town gas by natural gas might serve to explain why the spirit world no longer appears to be so active, although the idea of a spirit world still haunts some people.
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As an aside, here's a fun fact completely irrelevant to this question. This is an excerpt from a morbidly delightful book I read not too long ago: Molecules of Murder: Criminal Molecules and Classical Cases. (http://www.amazon.com/Molecules-Murder-Criminal-Classic-Cases/dp/0854049657)
Exposure to small but constant amounts of carbon monoxide over a period of time produces a variety of symptoms, which may at first not be recognized as having been caused by this gas. In addition to headaches and muscular pain there can be depression, chronic fatigue syndrome, and even hallucinations. In some instances this has been used to explain experiences associated with haunted houses, such as feelings of dread, sudden shivering, strange noises resembling footsteps, and even some unexplained deaths. In certain cases the haunting has been traced to a defective boiler or heater which is emitting carbon monoxide. Once the fault has been corrected these phantoms of the night are generally exorcised. The Victorian era was a golden age for haunting and weird manifestations, and one wonders to what extent this was a consequence of the widespread use of town gas (ed: http://en.wikipedia.org/wiki/Natural_gas#Town_gas) for lighting and cooking. this was piped to most homes and buildings and it inevitably contained a few percent of carbon monoxide. the replacement of town gas by natural gas might serve to explain why the spirit world no longer appears to be so active, although the idea of a spirit world still haunts some people.
I found this really interesting. Thanks :)
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Consider the following reactions:
O2-Hb + CO ::equil:: O2 + Hb + CO ::equil:: O2 + CO-Hb
When you increase the amount of oxygen (from ~20% in air to 100%), how is the equilibrium affected? Where would the increased oxygen concentration occur? Why might this be helpful in getting rid of the CO?
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Consider the following reactions:
O2-Hb + CO ::equil:: O2 + Hb + CO ::equil:: O2 + CO-Hb
When you increase the amount of oxygen (from ~20% in air to 100%), how is the equilibrium affected? Where would the increased oxygen concentration occur? Why might this be helpful in getting rid of the CO?
The oxygen causes the CO to break apart from the Hb and then the oxygen binds to it. So the Hb can now transprt oxygen to the body. But what happens to the CO? Do we just exhale it like CO2?
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Yes. Because both oxygen and carbon monoxide bind to the same site on hemoglobin, they compete for binding to hemoglobin and CO is therefore known as a competitive inhibitor. Since carbon monoxide binds hemoglobin very strongly, small concentrations of carbon monoxide can out-compete moderate concentrations of oxygen for hemoglobin binding. However, one feature of competitive inhibition is that very high concentrations of the substrate can out compete binding by the inhibitor. The way to think of this is that when carbon monoxide falls off of hemoglobin, there is so much oxygen present compared to carbon monoxide, that it is much more probable for oxygen to bind despite oxygen's lower affinity (it's not necessarily the case that the oxygen actively causes CO to break appart from the Hb, just that it prevents the reassociation by binding Hb before CO can). (For completeness, I'll also note that there are other types of inhibitors called allosteric inhibitors. These types bind to separate sites on hemoglobin and sometimes cannot be competed off by providing large amounts of substrate).
Now for your second question, the increased oxygen concentrations will be in the lungs, so the carbon monoxide falls off in the lungs where it can be exhaled.
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Yes. Because both oxygen and carbon monoxide bind to the same site on hemoglobin, they compete for binding to hemoglobin and CO is therefore known as a competitive inhibitor. Since carbon monoxide binds hemoglobin very strongly, small concentrations of carbon monoxide can out-compete moderate concentrations of oxygen for hemoglobin binding. However, one feature of competitive inhibition is that very high concentrations of the substrate can out compete binding by the inhibitor. The way to think of this is that when carbon monoxide falls off of hemoglobin, there is so much oxygen present compared to carbon monoxide, that it is much more probable for oxygen to bind despite oxygen's lower affinity (it's not necessarily the case that the oxygen actively causes CO to break appart from the Hb, just that it prevents the reassociation by binding Hb before CO can). (For completeness, I'll also note that there are other types of inhibitors called allosteric inhibitors. These types bind to separate sites on hemoglobin and sometimes cannot be competed off by providing large amounts of substrate).
Now for your second question, the increased oxygen concentrations will be in the lungs, so the carbon monoxide falls off in the lungs where it can be exhaled.
So would it be right to say that the oxygen breaks the equillibrium between the hb and CO?
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So would it be right to say that the oxygen breaks the equillibrium between the hb and CO?
Sure
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So would it be right to say that the oxygen breaks the equillibrium between the hb and CO?
Sure
Thanks :D
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I made a diagram, I'm not sure if it's correct ???
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fxs541.xs.to%2Fxs541%2F09300%2Fcarbon_monoxide_poisoning622.jpg&hash=a910189eaac42dbf8593d89849203cc20a402790)
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I made a diagram, I'm not sure if it's correct ???
(https://www.chemicalforums.com/proxy.php?request=http%3A%2F%2Fxs541.xs.to%2Fxs541%2F09300%2Fcarbon_monoxide_poisoning622.jpg&hash=a910189eaac42dbf8593d89849203cc20a402790)
Im not too sure either but i'd love to know if it's correct. it looks awesome by the way.
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Well... your equation is partially correct. When you burn carbon monoxide (with oxygen as the oxidant) you do in fact make carbon dioxide (and you apparently get a nice blue flame). Under physiological conditions, carbon dioxide will not be made from carbon monoxide and molecular oxygen. It is as described above: CO falls off hemoglobin and O2 preferentially binds thanks to the large concentration and Le Chatelier.
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I could be wrong, but I always thought carbon monoxide poisoning worked the following:
The the bond between heme and CO is stronger than the bond between heme and oxygen. The bond is much weaker for CO2 and heme.
The strong bond between heme and CO, results in the body taking in less oxygen. As the lungs do not exhale CO as efficiently as CO2, because of the strong heme and CO bond.
20% oxygenated air is not sufficient for the body, when poisoned by CO.
I suppose La Chatlier's principle affects the desorption of CO from the blood.
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I could be wrong, but I always thought carbon monoxide poisoning worked the following:
The the bond between heme and CO is stronger than the bond between heme and oxygen. The bond is much weaker for CO2 and heme.
The strong bond between heme and CO, results in the body taking in less oxygen. As the lungs do not exhale CO as efficiently as CO2, because of the strong heme and CO bond.
20% oxygenated air is not sufficient for the body, when poisoned by CO.
I suppose La Chatlier's principle affects the desorption of CO from the blood.
Yes, I would say that is an accurate description of the process (esp. the last sentence that 100% oxygen would increase desorption of CO from the blood).